A 60% sulfuric acid solution has a specific gravity (sg) of 1.5, NBR has an sg of 1.0 and FKM (Viton) 1.8. Therefore, NBR will float and FKM will sink in a 60% H2SO4 solution. Some people claim that the major motorcycle manufacturers will have changed the elastomer that they use for carburetor seals because ethanol blends have been used for such a long time. We believe this to be hearsay as we have tested many OEM parts and never found one that was FKM.